Lec11 Neisseria and gram negatives Flashcards
What types of bacteria does spleen play essential defense role?
encapsulated organisms
How can polysacccharide vaccines be altered to create longer lasting immunity? Why?
- by conjugating them to proteins
- this helps because proteins are more immunogenic than protein
What are the visual differences between meningococcus and pneumococcus both of which can cause meningitis?
pneumococcus: gram pos, diplococci
meningococcus: gram neg, kidney bean shaped cocci
Who gets meningitis?
- peak incidence age 6 mo to 2 years
- conditions of overcrowding
- those with splenectomy
- those with late complement deficiencies
Where does neisseria meningitis colonize? how is it transmitted?
- colonized nasopharynx in healthy people
- causes life-threatening infection when reaches bloodstream or CNS
- transmitted by respiratory droplets
What are the virulence factors of N. meningitis?
- secretes IgA protease
- —- allows survival in respiratory tract
- pili
- —- mediate attchement to respiratory epithelium
- Opa and Opc proteins
- —- allow to be engulfed by respiratory cells
- capsule
- — antiphagocytic
- lipooligosaccharide
- — endotoxin that triggers sepsis
What is rash like in mengingococcemia?
- cap appear as petechiae, purpura, or hemorrhagic bullae
- always non-blanching
WHat happens when LPS endotoxin released?
- released when bacterial cell dies
- riggers fatal downstream events
How many serogroups in N mengingitidis? which are most important?
- 13 serogroups
- determined by polysaccharide capsule
- most important A, B, C, W-135
Which serogroups are in the polyvalent vaccine?
A, C, Y, W-135
Why are vaccines against group B mengingococcus complicated?
- B has a polysacchardie capsule similar in struct to human sialic acid
besides meningitis, what other infections is neisseria meningitidis associated with?
- meningococcemia
- respiratory tract infection
- pneumonia
- otitis media
- conjuncitivitis
- septic arthritis
- pericarditis
What is treatment for n. meningitidis?
- cephalosporins [ceftriaxone] most common
- pencillin [one of few gram neg that does not produce beta lactamase]
What is empiric treatment of bacterial meningitis [when no organism on gram stain]?
- ceftriaxone [against meningococcus, haemophilus, and pneumococcus]
- vancomycin [because of beta-lactam resistant pneumococcal strains]
- sometimes steroids [to minimize inflammatory response]
- sometimes ampicillin [against listeria]
What is shape of listeria monocytogenes?
- gram positive rod
- tumbling end of end motility
Who is most susceptible to listeria?
- infants and elderly [bimodal distribution]
- immunocompromised
- pregnant women
What drugs do and do not have activity against l. monocytogenes?
- cephalosporins do not have reliable activity
- ampicillin does have activity
When is mengitis chemoprophylaxis used?
- for close contacts of index case
- can prevent invasive disease if given within 14 days of exposure
How do you differentiate N. gonorrheoeae and N. meningitidis?
- N gonorrhoeae does not have true polysaccharide capsule
- N. gonorrhoeae only utilizes glucose
- N. meningitidis utilizes glucose or maltose
What are the virulence factors for N. gonorrhoeae?
- similar to N. meningitidis
- pili assist binding human mucosal surfaces
Which patients are most at risk for N. gonorrhoeae?
- 15-25 year old men and women highest rate
- high risk in patients with terminal complement deficiencies
What are symptoms of gonorrhea?
about 10% asymptomatic
- infection of genitals
- foul smelling purulent discharge
- inflammation, redness, dysuria
What are the diseases associated with N. gonorrhoeae?
- ophtalmia neonatorum: transmitted from mother to child in delivery
- pelvic inflammatory disease
- pharyngitis
- perihepatitis [fitz-hugh-curtis syndrome]
What are symptoms of pelvic inflmmatory disease?
- chronic infection causes damage to fallopian tubes, sterility, ectopic pregnancy
What is used to diagnose gonorrhea [GC] and chlamydia?
- low sensitivity to culture
- use DNA probes
What is the treatment for N. gonorrhoeae?
- not penicillin [it has beta lactamase]
- increasing resistance to fluoroquinolones is major problem
- treat mostly with cephalosporins
- co-infection with chlamydia assumed
Where do we get L. monocytogenes?
from unpasturized cheeses
Where can you grow haemophilus?
- doesnt grow well on normal blood agar
- grows on chocolate agar that contains lyes RBCs
- grow on normal agar with factors V and X
- use satellite colonies
What is the satellite colonies technique for visualizing haemophilus?
- put on single streak of staph aureus
- make lawn of sample all around rest of plate
- staph aureus will cause hemolysis of RBCs and haemophilus can grow in this hemolytic zone
What is factor V?
- nicotinamide adenine dinucleotide [NAD]
- normally secreted by staph aureus
- needed for haemophilus growth in culture
what is factor X?
- hemin
- intracellular heme released by hemolysis of S. aureus
What diseases does H influenzae cause?
- meningitis
- otisis media
- sinusitis
- epiglotitis
- tracheobronchitis
- pneumonia
- bacteremia
What is the Hib conjugate vaccine made of?
- capsular polysacchardies contjugated to proteins
What disease associated wtih haemophilus ducreyii?
- STD chancroid: painful ulcer in association with enlarged tender lymph nodes
How does haemophilus ducreyii appear on slide?
school fish conformation
What are micro properties of moraxella catarrhalis [shape, gram, etc]?
- small gram negative
- diplococci
- catalase positive
- aerobic
What diseases does moraxella catarrhalis cause?
- otitis, sinusitis, pneumonia [especially in patients with emphysema]
usually upper respiratory infection
What are micro properties of bordetella pertussis? [shape, etc]?
- small gram negative
- coccobacillus
What does bordetella pertussis cause?
- whooping cough
What is DPT vaccine?
vaccine for diphtheria, pertussis, tetanus
What is virulence factor of bordetella pertussis?
A-B toxin
What is treatment for bordetella pertussis?
- usually just supportive
- in some situations use azithromycin
What are the 3 phases of whooping cough?
catarrhal: non-specific flu-like symptoms – non productive cough lasts 2 weeks, highly contagious
paroxysmal: repetitive coughing with whooping sound, vomitting, cyanosis
convalescent: paroxysmal cough gets slightly better, development of pneumonia, seizures, encephalopathy
What are the 3 encapsulated organisms that pts without spleen need to be vaccinated for?
- strep pneumoniae
- neisseria meningitidis
- haemophilus influenzae
What is the major cause of bacterial meningitis?
n. meningitidis
What is shape/micro features of neisseria meningitidis?
- gram negative
- diplococci
